The detection and testing for bearing wear is of importance, especially for canned pumps. Bearing wear may cause serious and expensive damage to the cans which contain the canned pumps, or to the pumps. Therefore, it is important to detect bearing wear before some catastrophic damage to the pump or motor occurs. Bearing wear detection devices and methods for this purpose are known. For example:
U.S. Pat. No. 1,788,941 to Bradley, et al, June 23, 1927, for Device For Indicating Undue Wear In Bearings employs a probe adjacent the connecting rod of an internal combustion engine. When the crankshaft bearing wears unduly, the resultant crankshaft departure from its usual motion is imparted to the probe, from which an indication of the excessive wear may be taken.
U.S. Pat. No. 3,542,494 to Sato Nov. 24, 1970, for Canned Motor Pump describes a bearing checking device in which a tube filled with inert gas under pressure is ruptured by a rotary shaft portion when bearing wear exceeds certain limits. The reduction in pressure in the tube is detected to indicate the excessive bearing wear.
U.S. Pat. No. 3,991,701 to Sato, Nov. 16, 1976, for Bearing Wear Detecting Device For Canned Motor Driven Pumps describes a chamber on the rotor which rotates about a fixed tube containing gas under pressure. Bearing wear causes the chamber to wear against the tube, rupturing the tube, which results in reduced gas pressure indicating the excessive bearing wear.
U.S. Pat. No. 4,095,552 to Lo, June 20, 1978, for Dummy Bearing For Bearing Wear Detection employs a dummy bearing structured to wear like the main bearing, either for thrust or radially, and the dummy bearing is directly inspected for excessive wear.
U.S. Pat. No. 4,175,331 to Johnson for Shaft Bearing Wear Measuring Apparatus Nov. 27, 1979, uses a probe attached to a transducer. When the probe is urged against the rotor shaft, a voltage may be detected by the transducer which indicates bearing wear.
U.S. Pat. No. 4,199,718 to Ikeda, et al, Apr. 22, 1980 for Bearing Wear Detector For AC Rotary Electric Instrument, suggests using three series connected coils spaced around poles driven by the rotor. Analysis of the voltage waves induced in the coils affords an indication of the bearing wear.
U.S. Pat. No. 4,320,431 to Bell, Mar. 16, 1982 for Fluid Circulating Pump describes a motor pump, suggests employing non-conductive bearings and conductive detecting rings held by the bearings disposed to be contacted by the motor shaft when bearing wear occurs. When the contact rings come into contact with the rotor, a circuit is completed indicating the wear and by setting off an alarm or halting operation of the motor.
Other patents generally related to bearing wear, for example, are:
U.S. Pat. No. 3,572,976 to Sato, Mar. 30, 1971 for Fluid Take-Off Device For Canned Motor Driven Pump, rotates a portion of the pumped fluid to the rotor in a fashion to reduce thrust bearing wear.
U.S. Pat. No. 3,637,329 to Sato, et al, Jan. 25, 1972, for Pump, describes a canned motor pump with means for using the pumped fluid to balance rotor thrust.